Having superior characteristics, aromatic polyesters that are represented by polyethylene terephthalate and polybutylene terephthalates are extensively used for manufacturing electric, electronic and automotive parts for example. However, their uses do not increase because of their low impact resistances. Therefore, it has hitherto been proposed to blend therein various kinds of polymers such as butadiene rubbers and acrylic elastomers. Among these blending methods, those with the copolymers being composed of such monomers as .alpha.-olefin and glycidyl ester of .alpha.,.beta.-ethylenically unsaturated acid that are mentioned in Japanese Laid-Open Patent Publication (Kokai) No. 32045/1977 and the U.S. Pat. No. 4461871 are comparatively superior to the others in improving effect of impact resistance and melt stability on molding. Nevertheless, in these methods, there is a problem that molded articles deteriorate in the impact resistance by hot-air aging in an oven. Further, the blendings of aromatic polycarbonates and acrylic elastomers to polybutylene terephthalates that are proposed in Japanese Laid-Open Patent Publication (Kokai) 500870/1980 are not satisfiable in impact resistance despite small increase and inferior in melt stability. No method solving the above-mentioned problems has been found.